Quantitative Analysis of Bisphenol A by Gas Liquid Chromatography H. H. GILL Analytical laboratories, The Dow Chemical ,A gas liquid chromatographic method permits the determination of bis(a,a dimethyl 4 hy2,4 droxybenzy1)phenol (EIPX) in 4 5 minutes. The procedure is applicable to the analysis of Bisphenol A containing 0.01% or more of BIPX. It can also be used for determining 2-(2-hydroxyphenyl)-2-(4-hydroxyphenyl) propane (o,p -BPA), and 4,4’-hydroxyphenyltrimethylchrornan (codimer) 2,2,4 by employing a loiiger chromatographic column than that used in determining BPX. Calibration curves for BPX are prepared by the analysis of samples containing .varying amounts of BPX, determined by the infrared method.
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B
A, 2-2-bis(4-hydroxyphenyl)propane, is used as a starting material in the production of epoxy resins and other polymers. The impurities present in Bisphenol A have been separated by pa,per chromatography and identified by Anderson, Carter, and Landua ( 1 ) . The principal impurities other than phenol were identified as: o,p’-BPA [2-(2-hydroxyphenyl) - 2 - (4 - hydroxylphenyl) propane], B P X [2,4-bis(C Y , adimethyl4-hydroxy benzyl) phenol 1, and codimer (4,4’ - hydroxyphenyl - 2,2,4 - trimethylchroman). Challa and Hermans later reported also on a method utilizing paper chromatography for the separation and measurement of the impurities in Bisphenol A ( 2 ) . Paper chromatography procedures of Anderson et al. ( 1 ) and Challa and Hermans ( 2 ) require concentration techniques to determine the impurities in 99+ % Bisphenol A . The analysis time also becomes important in the production of Bisphenol A. An analytical procedure was desired which xould provide an analytiis in less than 1 hour. Anderson et al. ( 1 ) reported what appeared to be extensive thermal decomposition of Bisphenol A by high temperature gas liquid chromatography. Recently Kanne and Stange (3) reported a gas liquid chromatographic procedure for free phenol in Bisphenol A. A gas liquid chromatographic (GLC) method for free phenol in Bisphenol h was developed and has been ISPHENOL
Co.,Midland, Mich. used since late 1960 in this laboratory. The speed of determining phenol (5 minutes) prompted the investigation of the gas liquid chromatographic technique as a quick procedure for the control of BPX. This impurity has the most influence in syntheses involving Bisphenol A. An infrared method in use by The Dow Chemical Co. for the determination of B P X in Bisphenol h provides reliable results within +0.0270.
phenol h for the impurities o,p’-BPA; codimer, and B P X (4). Attempts at direct analysis in this laboratory were not successful. Serious tailing of Bisphenol A in the chromatographic column prompted the investigation of a gas liquid chromatographic method after acetylation of all reactive hydroxyl groups in the Bisphenol A sample.
A sample is dissolved in a mixed solvent system (toluene-methanol). The Bisphenol A is precipitated by the addition of water. The organic layer is separated and the solvent evaporated. Dioxane is then added and the B P X is determined by its absorbance a t 12.8 microns. This procedure requires 1‘/2 hours for analysis.
Apparatus. A Beckman GC-2 gas chromatograph equipped with a Beckman hydrogen flame ionization detector was used. The recording device was a l-mv. Minneapolis-Honeywell, Model 14 recorder. Column Preparation. Columns were prepared from 0.125-inch 0.d. stainless steel tubing in lengths of 4 inches, 10 inches, and 3 feet. The packing used to fill the columns was 80/100-mesh Chromosorb W contain-
Tominaga has reported on the gas liquid chromatographic analysis of Bis-
EXPERIMENTAL
I
4
2
TIME, YIN.
Figure 1. Gas chromatographic determination of acetates of Bisphenol A and impurities No.
1 2 3 4 5
Compound Benzene plus phenyl acetate Codimer acetate o,p’-BPA acetate Bisphenol A acetate BPX acetate
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ul w
0
ba a
8
5w
a 7.0
No.
1
Gas chromatographic determination of acetates of Bisphenol A and No. 1
2 3
4
Campaund Benzene and phenyl acetate o,p'-BPA and codimer acetates Bisphenol A acetate BPX acetate
ing 25% by weight of L.1C-2R-446 (Cambridge Industries Co., Inc., Cambridge, Mass.) and 27, phosphoric acid (85%). Chromatograph Conditions. The column temperature was maintained a t 240" C. The column inlet temperature is not controlled on the Recknian GC-2, but measurement indicated i t to be about 250" C. Helium flow rates in milliliters per minute through the three columns were: 3foot column, 72; 10-inch column, 94; 4-inch column, 125. Procedure. A 1-gram sample of Bisphenol A was dissolved in a mixture of 3 ml. of pyridine a n d 3 ml. of acetic anhydride. The mixture was placed on a steam bath for 20 minutes. Upon removal from the bath, 10 ml. of water and 3 ml. of concentrated hydrochloric acid were added and the solution was allowed to cool. Two milliliters of benzene were then added from a pipet and the mix-
ture was shaken vigorously. a4fter mixing, the layers were allowed to separate. Chromatograms of the benzene extract containing the acetylated Bisphenol A and impurities were then obtained, using a 3-~1.sample. RESULTS AND DISCUSSION
In preliminary work, acetyl chloride was used as the acetylating agent. With this reagent and purified Bisphenol A, extraneous peaks appeared in the chromatogram, probably because compounds other than acetylated phenolics were formed by acid-catalyzed sidf reactions. When acetic anhydride was used in the absence of pyridine, these side reactions were increased. It was felt this was because in acetylation with acetyl chloride, most of the hydrochloric acid formed is volatilized from the solution, whereas the acetic acid formed in the acetylation with acetic
GLC Response for BPX in Bisphenol A GLC response . Peak % BPX, IR Att. height Table 1.
No.
1202
0.01 0.04 0.07 0.19
2 2 2
0.33 0.55
10
ANALYTICAL CHEMISTRY
5 5
x x x
102 102 102 102
49
x
102 102
80 65
x x
3 11.5 22
TIME,YIN.
Figure 3. Gas chromatographic determination of BPX acetate in Bisphenol A acetate
2
Figure 2. impurities
I4
Peak height at 2 X lo2 3
ii.5 22 122 200 325
Compound Benzene, phenyl acetate, codimer acetate, and o,p'-BPA acetate BPX acetate
anhydride remains in solution. This would produce,a higher acid concentration in the acetic anhydride acetylation. The use of pyridine in the acetic anhydride acetylation prevents these unwanted reactions by lowering the acidity of ,the system. Figure 1 illustrates the chromatogram obtained using the 3-foot column of a Bisphenol h sample containing o,p'BPA, codimer, and BPX. Free phenol as phenyl acetate appears with the benzene solvent peak. This column separates all components but is not useful where rapid analysis is necessary. Figure 2 illustrates the chromatogram obtained on a Bisphenol A sample containing impurities. using the 10-inch column. Under the conditions of analysis, the o,p'-BPA acetate and the codimer acetate are not separated. B P X acetate appears a t 36 minutes, which, considering reaction time to acetylate, offers no advantage over the 1'/2-hour infrared procedure. Figure 3 illustrates the chromatogram obtained using the 4inch column. This column does not separate o,p'-BPA, codimer, and Bisphenol -4 acetates but does provide a procedure for the quick determination (45 minutes) and control of B P X in the production of Bisphenol A. The B P X acetate appears a t 13 minutes. To calibrate the peak heights for BPX, six samples of Bisphenol A previously analyzed by infrared were used as standards and were analyzed by the described procedure. Table I lists the results obtained. A plot of peak height us. percentage of B P X by the infrared method gives a curve which deviates from linearity at the lower percentages [ress than 0.1). Data read from the plot shouM not differ from
infrared values by more than the probable error of the infrared method. When a straight line is passed through the origin and the upper points, the deviation in the lower Fercentage range is less than twice the probable error Of the infrared data. I t is not known
whether this deviation is due to the limits of the infrared procedure or linearity deviation in the GLC method. LITERATURE CITED
(1) Anderson, W. M., Carter, G. B., Landua, A. J., ANAL.CHEM.31, 1214
(1959).
( 2 ) Challa, G., Hermans, P. H., Zbid., 32, 778 ( l g 6 0 ) . ( 3 ) Kanne, F., Stange, K., Z. ANAL.CHEM. 189,261-5(1962). ( 4 ) Torninaga, Sachiyuki, Bunseki Kagaku 12 ( 3 ) , 137-43 (1963).
RECEIVEDfor review October 4, 1963. Accepted February 19, 1964.
Selective Liquid-Liquid Extraction of Radiotin with 2-Thenoyltrifluoroacetone JAMES R. STOKELEY' and FLETCHER L. MOORE Analytical Chemistry Division, Oak Ridge National laboratory, Oak Ridge, Tenn.
b A new, rapid, highly selective liquid-liquid extraction method for radiotin is based on the extraction of radiotin from a sulfuri'c acid-chloride aqueous medium with 0.5M Z-thenoyltrifluoroacetone-methyl isobutyl ketone. Tartaric acid or sulfuriic acid readily strips the tin from the organic phase. The method has been employed successfully in the radicichemical purification and isolation of radiotin from both old and new fission product mixtures. A redetermination of the half life and gamma spectral characteristics of tin-1 28 is reported.
T
lack of completely satisfactory separation methods for radiotin has been discussed in a recent review (9). Precipitation and distillation procedures are not completely selective and are tedious, time-consuming, and cumbersome. Liquid-liquid extraction is often a desirable separation method, because of its speed and adaptability for use with both tracer and macro levels of ions. However, a highly selective solvent extraction method for radiotin has not been previously reported, with the possible exception of .,he method of Pappas (10) which is based on the extraction of tin(I1) clithionate with little regard for high yield. Because of the successful use of the versatile chelating agent, thenoyltrifluoroacetone (TTA), by many radiochemists (8, I I ) , the writers investigated its possible application in the selective liquid-liquid extraction of radiotin. TTA has previously proved t o be a highly selective extractant for other quadrivalent metal ions from solutions of relatively high acidity (8). HE
EXPERIMENTAL
Apparatus. Vortex test tube mixer, Model K-500-4, supplied by Scientific Industries, Inc., Springfield, Mass.
NBI(T1) well-type gamma scintillation counter, 13/4X 2 inches. Gamma scintillation pulse height analyses were performed with a 256channel pulse-height analyzer coupled to a 3 X 3 inch NaI(T1) detector. Samples were counted on a 1.23-gram per sq. cm. beryllium beta absorber. Beta counting was done with a methaneflow proportional counter. Reagents. Analytical grade reagents were used without further purification. T h e 2-thenoyltrifluoroacetone (TTA, M.W. 222) was supplied bv the Columbia Organic Chemicals C'o., Columbia, S. C . The 0.5M TT.4-methvl isobutvl ketone (hexone) was pre-kquilibratid with an equal-volume portion of I N hydrochloric acid solution. Procedure. If the sample is a uranyl salt, dissolve in a minimal amount of concentrated hydrochloric acid which contains sufficient tin(1V) chloride so t h a t t h e final aliquot preferably does not contain more t h a n 0.2 mg. of tin per ml. Heat just below boiling for a few seconds to ensure exchange. Adjust the aqueous solution t o a concentration of 1 to 2N hydrochloric acid, 1 to 2N sulfuric acid, and approximately 1 volume % hydrogen peroxide. Extract for 2 minutes with a n equal-volume portion of O.jlk' TTA-methyl isobutyl ketone, using a Vortex mixer or other suitable extraction technique. Centrifuge for 1 minute in a clinical centrifuge. Draw off and discard the aqueous phase. Carefully wash the sides of the extraction vessel with several milliliters of a 1.2N sulfuric acid-2M ammonium chloride solution, Draw off and discard the aqueous phase. Scrub the organic phase by mixing for 1 minute with a n equal-volume portion of a solution made up of 1.2N sulfuric acid-2M ammonium chloride and 1 volume % hydrogen peroxide. Centrifuge and discard the aqueous phase. Repeat the scrub step once. Strip the tin from the organic phase by extracting with a n equal-volume portion of 1Jf tartaric acid for 10 minutes. Centrifuge for 1 minute, and use a n aliquot of the aqueous strippant for radioactivity measurements. If a yield
determination for tin is desired, the spectrophotometric method of Luke (4,5 ) i i useful. RESULTS A N D DlSCUSSlON
Two stock solutions of tin-113 tracer were prepared for the evaluation of pertinent variables. One solution contained 15 pg. of inactive tin per ml. in 5N hydrochloric acid; the other contained 20 pg. of inactive tin per ml. in 6 N sulfuric acid. All counting was done a t least 18 hours after the final separatbn in order to allow the tin-113 daughter, 1.73-hour indium-] 13m, to grow into equilibrium. Extraction Characteristics. Preliminary experiments indicated t h a t reasonable amounts of tin-1 13 tracer could be extracted only from chloride media; moreover, a polar solvent was necessary for the TT.4. An almost direct correlation was found between increased extraction and solvent polarity. Less than 1% of the tin113 tracer was extracted by 0.5M T T I in xylene, while more polar solvents, such as nitrobenzene, raised the extraction to approximately 60%. Hexone, when used as the solvent for TTA, extracted tin essentially quantitatively from an aqueous phase which was greater than 0.5N in hydrochloric acid. Diisobutyl ketone, a likely substitute for hexone, extracted approximately 50% of the tin-113 tracer under identical conditions. Figure 1 shows the extraction of tin113 tracer into 0.5M TTA-hexone as a function of hydrochloric acid concentration. Aqueous solutions of varying hydrochloric acid content, containing 1% hydrogen peroxide and tin-1 13 tracer (2.5 X lo4 gamma c.p.m.), were extracted for 2 minutes at room temperature with equal-volume portions of 0.5M TTA-hexone. Vortex test tube mixers were employed. After centrifuPresent address, Chemistry Ile artment, Clemson College, Clemson, S.
8.
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